Nonphytate phosphorus requirement and phosphorus excretion of broiler chicks fed diets composed of normal or high available phosphate corn with and without microbial phytase

A study was conducted to evaluate the ability of the young (0 to 3 wk) broi ler chicken to utilize the P provided by a high available P corn [HAPC; 0.2 7% total P and 0.17% nonphytate P] in comparison with yellow dent corn (YDC ; 0.23% total P and 0.03% non-phytate P), and to determine the extent to wh ich supplementation with exogenous phytase enzyme could reduce the demands for dietary P and subsequently reduce P excretion. Diets prepared using the two types of corn differed in the amount of phytate-bound P, with the HAPC diets containing approximately 50% less phytate-bound P. Treatment diets w ere prepared by varying the amount of dicalcium phosphate, and ranged from 0.10 to 0.50% nonphytate P for YDC diets, and from 0.18 to 0.50% nonphytate P for HAPC diets. Sublets of each diet were supplemented with 800 units/kg phytase. Each diet was fed to six pens of five male chicks of a commercial broiler strain from 1 to 21 d of age. Regression analysis was used to esti mate nonphytate P requirements for each corn type with and without phytase supplementation. The greatest need for nonphytate P was for maximum tibia ash, with requirem ents of 0.39, 0.29, 0.37, and 0.32% in diets with YDC, YDC plus phytase, HA PC, and HAPC plus phytase, respectively. Addition of phytase liberated appr oximately 50% of the phytate-bound P from each diet. These levels were suff icient to support body weight, feed conversion, and livability. Fecal P con tent of broilers fed diets with YDC at the NRC (1994) recommended level of 0.45% nonphytate P was 1.21%, whereas at the respective requirement points indicated above, the P content was 1.09, 0.87, 0.78, and 0.64% in feces fro m broilers fed diets with YDC, YDC plus phytase, HAPC, and HAPC plus phytas e, respectively. Thus, fecal P output could be reduced while maintaining op timum performance by the use of reduced dietary nonphytate P, introduction of HAPC, and phytase supplementation. One of the greatest benefits of phyta se supplementation appeared to be maintaining livability at lower dietary l evels of nonphytate P.